1. Technical Field
The present invention relates to data storage systems in general, and more particularly, to data storage systems having shared tape drives. Still more particularly, the present invention relates to method and apparatus for providing continuous access to shared tape drives from multiple virtual tape servers within a data storage system.
2. Description of Related Art
In a hierarchical data storage system, expensive and fast access storage devices are commonly paired with arrays of cheaper and relatively slower access data storage devices. Expensive and high-speed storage devices can be, for example, direct access storage devices (DASDs), while cheaper and slower storage devices can be, for example, tape drives.
A virtual tape storage system is a hierarchical data storage system. A virtual tape storage system may include one or more virtual tape servers (VTSs) along with one or more tape storage and retrieval systems such as the TotalStorage® 3494 Enterprise Tape Library manufactured by the International Business Machines Corporation of Armonk, N.Y.
During operation, a virtual tape storage system may communicate with one or more host computers. However, a conventional VTS within a virtual tape storage system does not support operations in a multi-node environment. Thus, when there is a malfunction within a conventional VTS, it is very difficult to locate the source of the problem. The process of identifying and correcting a problem often involves customer technical support team, support center, VTS developers, etc. VTS down time, in many cases, is disruptive to customers. Consequently, it would be desirable to provide a method for managing multiple controllers that share multiple tape drives within a data storage system such that continuous access can be provided to the shared tape drives from multiple controllers.